Auto merge of #4335 - debris:rebased_4021, r=matklad

Rebased and fixed 4025: Apply --all if workspace is virtual

- fixes #4021
- rebased #4025
- fixed issue issue described by @matklad in https://github.com/rust-lang/cargo/pull/4025#pullrequestreview-40660570
- added test `build_virtual_manifest_one_project` which covers the fix